btrfs: make extent_range_clear_dirty_for_io return void

Does not return any errors, nor anything from the callgraph. There's a
BUG_ON but it's a sanity check and not an error condition we could
recover from.

Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent_io.c

@@ -1451,7 +1451,7 @@ int unlock_extent(struct extent_io_tree *tree, u64 start, u64 end)
 				GFP_NOFS);
 }
 
-int extent_range_clear_dirty_for_io(struct inode *inode, u64 start, u64 end)
+void extent_range_clear_dirty_for_io(struct inode *inode, u64 start, u64 end)
 {
 	unsigned long index = start >> PAGE_CACHE_SHIFT;
 	unsigned long end_index = end >> PAGE_CACHE_SHIFT;
@@ -1464,7 +1464,6 @@ int extent_range_clear_dirty_for_io(struct inode *inode, u64 start, u64 end)
 		page_cache_release(page);
 		index++;
 	}
-	return 0;
 }
 
 int extent_range_redirty_for_io(struct inode *inode, u64 start, u64 end)

fs/btrfs/extent_io.h

@@ -338,7 +338,7 @@ int map_private_extent_buffer(struct extent_buffer *eb, unsigned long offset,
 		      unsigned long min_len, char **map,
 		      unsigned long *map_start,
 		      unsigned long *map_len);
-int extent_range_clear_dirty_for_io(struct inode *inode, u64 start, u64 end);
+void extent_range_clear_dirty_for_io(struct inode *inode, u64 start, u64 end);
 int extent_range_redirty_for_io(struct inode *inode, u64 start, u64 end);
 void extent_clear_unlock_delalloc(struct inode *inode, u64 start, u64 end,
 				 struct page *locked_page,